Starting mechanism for fluorescent lamps



Much 28, 1944. I 1 A G MUELLER 2,345,414

STARTING MECHANISM FOR FLUORESCENT LAMPS Filed April 25, 1940 Adolf G. MQeHer',

Their Attorney.

taken along the line 3-3 Patented Mar. 28, 1944 2,345,414 STARTING MECHANISM FOR FLUORESCENT LAMPS Adolf G. Mueller, Stratford, Conn, minor to General Electric Company, a corporation of New York Application April 25, 1940, Serial No. 331,566 3 Claims. (Cl. 200-142) This invention relates to starting mechanisms for electric discharge devices, and more particularly to a starting mechanism for a fluorescent lamp of the well-known commercial type now in use.

An object of the invention is to provide an improved starting switch formed with a housing and connecting means such that it may be readily connected and disconnected from the lamp operating mechanism.

In the accompanying drawing Fig. 1 is a. view a fluorescent lamp and associated starting mechanism constructed in accordance with this invention; Fig. 2 is an elevational view of the starting mechanism and supporting socket therefor; Fig. 3 is a view of the supporting socket of Fig. 2; Fig. 4 is an exploded view showing the details of the starting mechanism; Fig. 5 is a diagrammatic view showing the manner in which the starting mechanism and fluorescent lamp are connected in circuit, and Fig. 6 is aperspective view of the supporting socket for the starting mechanism.

Referring to the drawing, Fig. 1 illustrates an electric discharge device such as a. fluorescent lamp I 0 supported at each end on sockets l I, the sockets themselves being mounted on a supporting strip or reflector base I2 of a lamp flxture, or the like. This is one of the ways employed in mounting a fluorescent lamp in fixtures or reflectors for use in a wide variety of installations. Fluorescent lamps of the type mentioned require a starting switch for applying current to the cathodes of the lamp to heat them to a point at which they become emissive, and an impedance, such as a reactor, to limltthe current flow through the cathode. Once the cathodes are heated a discharge are is struck between them thereby lighting the lamp and shorting out the switch.

It is desirable to mount the starting mechanism at a point where it is easily accessible for installation or replacement since in some cases it has been found that failure of the fluorescent lighting systems is due to failure of the starting switch. Failure of the reactor rarely, if ever, occurs inasmuch as the latter is constructed of relatively rugged material and seldom needs attention. If provision is made for easy replacement of the starting switch it is possible to take care of most cases wherein shutdown of the lamp is due to failure of the starting system.

To this end, a mounting socket I3 is provided to receive a starting switch mechanism It, and these elements are constructed with coacting contact means so designed that the switch mechanism may easily be connected and disconnected from the mounting socket I3. Removal of the switch mechanism is accomplished simply by grasping it in the hand and turning it within the socket member. The socket I3 may be mounted at any convenient point, preferably adjacent the fluorescent lamp; by way of example it has been shown mounted on the reflector surface [2. Referring to Fig. 4, the starting switch may be of the glow discharge type, for example, a switch such as that disclosed in the copending application of Wayne C. Smitley, Serial No. 289,897, filed August 12, 1939, and assigned to the same assignee as the instant application. The switch elements are contained within a sealed glass envelope l5 through which lead line It and I! conduct current to a pair of contacts l8 and I8. The contact I8 is formed by a bent-over extension of the lead-in wire l6, while the contact [9 is a separate piece of wire mounted on a U-shaped bimetallic element 20 carried by the other lead-in wire [1. A piece of emissive material 2| is placed on the bimetallic strip adjacent the bent-over extension of the lead-in wire 16 to increase the glow discharge between these two elements.

As shown in the circuit diagram of Fig. 5, the glow discharge switch is placed in series with one of the terminals of the filament at each end of the fluorescent lamp. The other terminals of the filaments are placed in series with a reactor R and the lead lines of a power circuit. A switch S controls power to the assembly. Upon closure of the switch S current flows through the reactor R and the left-hand filament of the lamp and thence to the lead-in wire l6, and a glow discharge takes place between this lead wire and the bimetallic trip secured to the lead wire ll so that current is conducted to the right-hand fllament of the lamp and thence to the other side of the power line. The glow discharge between the lead wire l6 and the bimetallic strip at a point adjacent the emissive material 2| heats up the bimetallic strip 20 and causes it to flex in a manner to close the contacts l8 and I9. Closure of these contacts applies full line voltage to the lamp filaments beating them to a point at which they give off an electron discharge. Closure of the contacts likewise shorts out the glow discharge arc permitting the bimetallic strip to cool. lag in the it remain to 2 seconds after coolinitiated during which However, due to the slight thermal bimetallic strip the contacts l8 and closed for the order of ing of the strip has been a supporting plate time the lamp filaments are being heated in the manner aforementioned. When these contacts open, the circuit through the lamp filaments is interrupted and the reactor produces an inductive surge across the filaments. This results in an arc discharge taking place between the fila= ments of the lamp so that the lamp lights. When this occurs current from the power line flows directly through the lamp arc shunts out the glow switch. In addition to pro viding an inductive surge for starting the lamp, the reactor limits the current through the ills.- ments during the lamp during its operation. If desired, a small condenser C of approximately .006 mid. may be placed across the lead-in wires it and ill to prevent radio interference.

In orderto provide a housing for the. glow switch to facilitate easy connection with the support it, the glass envelope is is enclosed within a cylindrical. metal casing 26 having a liner of insulating material 25. The open end of the casing 26 is closed by means of an insulating fiber disk 25 provided with two spaced contact prongs 2i for electrical connection with the socket l3 in a manner to be described later. The condenser C is likewise enclosed within the casing 26 in a position immediately adjacent the glass envelope at. In some cases it has been found that failure of the contacts it and it to close has resulted in prolonged heating of the glow switch under the action of the glow discharge between the lead-in wires it and H. This may cause serious damage when the generated heat is confined within the casing 26. In order to prevent overheating of the switch mechanism and possible damage to the surrounding supporting structure, a fusible element as mounted on 29 of insulating material is likewise disposed within the casing 2d. The ruse link 28 is responsive to the ambient temperature within the housing 2 3. Should the glow switch operate an undue length of time such as to cause possible burning or damage to the supporting structure, the fuse 28 will melt cutting ofi the supply of current to the glow switch. This is accomplished due to the fact that the fuse link is connected electrically in series with the starting glow switch, as shown in Fig. 5. In manuiacture, the plate 29 is provided with a window 29 which frames the fuse link and provides space for the metal to separate upon melting of the link. The assembled plate and fuse link are dipped in a rosin lacquer. Upon melting of the link separation of the ends of the metal is facilitated by thecapillary action of the lacquer layer, thereby efiectively preventing arcing across the link.

Each of the contact prongs 2! is formed of a hollow pin or rivet so, one end of which is peened over the disk 26 to secure it in position, and the other end of which is formed with an enlarged head 3i provided with a peripheral groove 82. In manufacture the condenser C is provided with lead wires 33 and 86 which are connected electrically in parallel with the switch mechanism and fusible element. To this end, the wires it and 33 are connected to one of the contact prongs 27. This is accomplished by inserting these wires within the hollow rivet and fastening them in position by a drop of solder which flows down into the hollow rivet making a good electrical connection therewith. The lead-in wire ll is then connected; to one of the fusible element,

oi the lead wires-'35 discharge and asst,

the heating period and through while to fusible element are did the other lead wire of this element and the lead 3B of the capacitance are connected to the other contact prong 2'6 by a solder joint in the manner just descrimd. After the lead wires oi the glow switch, capacitor and fusible element are connected to the contact prongs 27, the as= sembly is inserted within the housing 2% and the insulating disk 26 secured to the bottom of the housing by turning over lugs to the edge of the container 2 3; the lugs rest in slots 3? in the disk 25.

The supporting socket i3 is formed with a housing so of insulating material, such as a phenolic condensation product and filler; the housing, in turn. is provided with an annular recess ill for receiving the container 24.- The bottom 32 of the recess is formed with two annularly arranged keyhole slots 63 for receiving the connector prongs H. The enlarged ends st of the connector prongs extend through the keyhole slots and engage spring contact members 6t mounted on the bottom of the housing to and disposed at points adjacent the walls of the keyhole slots. Contact elements l i are formed of spring wire which rest in the grooves 32 formed on the enlarged ends of the contact prongs. The container 2 3 is locked securely within the mounting socket simply by placing it in the recess ll, inserting the enlarged ends of the connector prongs 21 through the large openings in the keyhole slots and then slightly rotating the container to move the ends of the prongs be- .neath the narrower portions of the keyhole slots. In this position the switch prongs are in good electrical contact with the wire contact elements so since the latter are spring biased into engagement with the grooves 32. The spring contacts firmly engage the switch prongs and prevent the container 2 3 from being turned in the recess. This is accomplished by bending the wires 416 into the planes of the keyhole slots to form projections 65 which engage the rims oi the prongs and hold them in seated portion, as shown in Fig. 3. The prongs are snapped past these projections upon rotation of the switch container.

The wire contacts Gil rest in shallow recesses 36 formed in the bottom of the housing as and are electrically connected to terminal plates ill disposed at opposite ends of the housing in grooves 68; these electrical connections may be made by spot welding, soldering, or the like. Each of the terminal plates ll is provided with a terminal screw (it for receiving a connecting wire of the lamp circuit. In order to hold the terminal plates ill and the contact wires 34 in position on the base, the recesses 65 and grooves le are closed by means of an insulating cover plate' 50 formed of sheet fiber, or the like. The cover plate is held in position by drive screws 5i. To facilitate mounting of the housing on any supporting surface, it is formed at opposite ends with openings 52 for the reception of any suitable fastening means.

The invention makes possible an arrangement wherein the starting switch of a fluorescent lighting system may be easily assembled in the system and may be readily replaced in case of failure without disturbing the associated lamp fixtures or reflectors of the system. Such would not be I the case if the starting switch were permanently wired into the system. In addition, the container it provides a protective casing for the relatively fragile glow switch. Inasmuch as the glow switch is compact and the capacitor and of small size. these members extending from ing the operation may be assembled in a container of reduced size such that the switch may be installed in the small amount of space available in a lamp fixture. 'Ihecapacitance C is utilized to reduce radio interference but, manifestly, in some cases, it may be omitted. Similarly, if desired, the fusible element may be omitted without affectof the glow switch.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In a starting mechanism for a discharge lamp, a housing having contact means adapted to engage the contacts of a receptacle, a switch mechanism confined within said housing including thermally responsive contact members operated by the heat of a glow discharge therebetween to control the flow of current to the lamp, a circuit interrupting means likewise confined within said housing and being electrically connected in series with said switch mechanism, said means being operable in response to increase in the ambient temperature within said housing upon continued unwarranted operation of said glow discharge to interrupt the flow of current through the switch.

2. In a starting means for a discharge lamp, a housing provided with contact means adapted to engage the contacts 01' a receptacle, an ento heat said contact means, and a fusible element disposed within said housing acfiacent said envelope and being electrically connected in series ature within said housing upon continued 1m warranted flow of current in the starting circuit to interrupt the flow 01' current through the switch.

ADOLF G. MUELLER. 

